The present invention is directed to a single step process of forming a coordination catalyst composition by contacting a bidentate or a tridentate ligand forming compound, a transition metal compound and an inorganic oxide support-activator agglomerate. Further, the present process provides a coordination catalyst composite which does not require the initial formation and isolation of a bidentate or tridentate transition metal chelate nor the need to treat said chelate with a conventional cocatalyst compound (e.g. MAO, boranes or borates) to provide an active catalyst composition. The absence of such cocatalysts eliminates the need to handle flammable or hazardous compounds.
Coordination catalyst systems, which are usually based on transition metal compounds of Group 3 to 10 and organometallic compounds of Group 13 of the Periodic Table of the Elements, are an exceptionally diverse group of catalysts which are employed in chemical reactions of olefinically unsaturated compounds for the preparation of olefin polymers by coordination polymerization.
The preparation of polyethylene of increased density (high-density polyethylene, HDPE) and of polymers and copolymers of ethylene, propylene or other 1-alkenes is of considerable industrial importance. The use of organometallic catalyst for preparation of such polymers and copolymers has become of increasing interest.
The prevailing belief on the reaction mechanism of coordination catalysts is that the transition metal of the catalyst compound forms a catalytically active center to which the olefinically unsaturated compound bonds by coordination in a first step. Olefin polymerization takes place via coordination of the monomers and a subsequent insertion reaction into a transition metal-carbon or a transition metal-hydrogen bond.
The presence of activator compounds (e.g., organoaluminum compounds such as methylalumoxane) as part of coordination catalyst systems or during the catalyzed reaction is thought to be necessary in order to activate the catalyst. The chelate compound containing the transition metal atom is typically referred to as a “pre-catalyst.” The required presence of certain compounds (e.g. MAO) known to be capable of causing alkylation of the transition metal atom and subsequent abstraction of hydrocarbyl group is believed required to provide an active catalytic site with respect to the pre-catalyst. Such compounds are typically referred to as “co-catalysts” and are selected from alkyl alumoxanes or certain borane or borate compounds. The combination of a pre-catalyst with a co-catalyst is believed required to provide an active catalytic complex system, generally referred to as a “primary catalyst”. These co-catalysts have certain drawbacks which have inhibited the use of the resultant complex in commercial applications. The alumoxanes are pyrophoric and require special handling when used. The borane and borate co-catalysts, although easier to handle, are more expensive due to their formation from reagents that are difficult to handle. Because each of the co-catalysts is used in large amounts to form a resultant catalytic complex system, the concerns related to each is substantial.
The best known industrially used catalyst systems for coordination polymerization are those of the “Ziegler-Natta catalyst” type and the “Phillips catalyst” type. The former comprise the reaction product of a metal alkyl or hydride of an element of the first three main groups of the Periodic Table and a reducible compound of a transition metal element of Groups 4 to 7. The combination used most frequently comprises an aluminum alkyl, such as diethylaluminum chloride and titanium (IV) chloride. For example, it is known that highly active Ziegler-Natta catalysts are systems in which the titanium compound is fixed chemically to the surface of magnesium compounds, such as, in particular, magnesium chloride.
The Phillips Process for ethylene polymerization developed around Phillips catalyst that is composed of chromium oxide on silica as the support. This catalyst was developed by Hogan and Banks and described in U.S. Pat. No. 2,825,721, as well as A. Clark et al. in Ind. Eng. Chem. 48, 1152 (1956). Commercialization of this process provided the first linear polyalkenes and accounts for a large amount of the high-density polyethylene (HDPE) produced today.
More recent developments have focused on single-site catalyst systems. Such systems are characterized by the fact that their metal centers behave alike during polymerization to make very uniform polymers.
Catalysts are judged to behave in a single-site manner when the polymer they make meets some basic criteria (e.g., narrow molecular weight distribution, or uniform comonomer distribution). Thus, the metal can have any ligand set around it and be classified as “single-site” as long as the polymer that it produces has certain properties. Includable within single-site catalyst systems are metallocene catalysts and constrained geometry catalysts.
A “metallocene” is conventionally understood to mean a metal (e.g., Zr, Ti, Hf, Sc, Y, Vi or La) complex that is bound to at least one cyclopentadienyl (Cp) rings, or derivatives thereof, such as indenyl, tetrahydroindenyl, fluorenyl and mixtures. In addition to the two Cp ligands, other groups can be attached to the metal center, most commonly halides and alkyls. The Cp rings can be linked together (so-called “bridged metallocene” structure), as in most polypropylene catalysts, or they can be independent and freely rotating, as in most (but not all) metallocene-based polyethylene catalysts. The defining feature is the presence of two Cp ligands or derivatives thereof.
Metallocene catalysts can be employed either as so-called “neutral metallocenes” in which case an alumoxane, such as methylalumoxane, is used as an activator or they can be employed as so-called “cationic metallocenes” which incorporate a stable and loosely bound non-coordinating anion as a counter ion to a cationic metal metallocene center. Cationic metallocenes are disclosed in U.S. Pat. Nos. 5,064,802; 5,225,500; 5,243,002; 5,321,106; 5,427,991; and 5,643,847; and EP 426,637 and EP 426,638.
“Constrained geometry” is a term that refers to a particular class of organometallic complexes in which the metal center is bound by only one modified Cp ring or derivative. The Cp ring is modified by bridging to a heteroatom such as nitrogen, phosphorus, oxygen, or sulfur, and this heteroatom also binds to the metal site. The bridged structure forms a fairly rigid system; thus the term “constrained geometry”. By virtue of its open structure, the constrained geometry catalyst can produce resins (long chain branching) that are not possible with normal metallocene catalysts.
The above-described single site catalyst systems are primarily based on early transition metal d° complexes useful in coordination polymerization processes. However, these catalysts are known to be oxophilic and, therefore, have low tolerance with respect to even small amounts of oxygenated impurities, such as oxygen, water and oxygenated hydrocarbons. Thus these materials are difficult to handle and use.
More recently, late transitional metal (e.g., Fe, Co, Ni, or Pd) bidentate and tridentate catalyst systems have been developed. Representative disclosures of such late transition metal catalysts are form in U.S. Pat. No. 5,880,241 and its divisional counterparts U.S. Pat. Nos. 5,880,323; 5,866,663; 5,886,224; 5,891,963; 6,184,171; 6,174,976; 6,133,138, and PCT International Application Nos. PCT/US98/00316; PCT/US97/23556; PCT/GB99/00714; PCT/GB99/00715; and PCT/GB99/00716.
It is commonly believed that both single site and late transition metal pre-catalysts typically require activation to form a cationic metal center by an organometal Lewis acid (e.g., methyl alumoxane (MAO)) (characterized as operating through a hydrocarbyl abstraction mechanism). Such activators or cocatalysts are pyrophoric (or require pyrophoric reagents to make the same), and are typically employed in quantities which are multiples of the catalyst. Attempts to avoid such disadvantages have led to the development of borane (e.g., trispentaflurophenylborane) and borate (e.g., ammonium tetrakispentaflurophenylborate) activators that are non-pyrophoric but more expensive to manufacture. These factors complicate the development of heterogeneous versions of such catalyst systems in terms of meeting cost and performance targets.
Use of these chelated transition metal pre-catalysts and related types in various polymerization processes can give products with sometimes extremely different properties. In the case of olefin polymers, which are generally known to be important as commercial materials suitable for a variety of applications depending on the one hand, on the nature of the monomers on which they are based and on the choice and ratio of comonomers and the typical physical parameters which characterize the polymer, such as average molecular weight, molecular weight distribution, degree of branching, crosslinking, crystallinity, density, presence of functional groups in the polymer and the like and on the other hand, on properties resulting from the process, such as the degree of branching of the resultant polymer structure, content of low molecular weight impurities, presence of catalyst residues, and, last but not least on costs.
In addition to realization of the desired product properties, other factors are decisive for evaluating the efficiency of a coordination catalyst system, such as the activity of the catalyst system, that is to say the amount of catalyst required for economic conversion of a given amount of olefin, the product conversion per unit time and the product yield. Catalyst systems such as the Fe or Co catalysts described herein, which exhibit high productivity and high specificity in favor of a low degree of branching of the polymer, are sought for certain applications, such as blow molding and the like. Catalyst systems utilizing the Ni and Pd catalysts, also described herein, seek to achieve highly branched polymers with reasonable productivity.
The stability and ease of handling of the catalyst or its components is another factor that affects the choice of commercial embodiments thereof. Practically all known coordination catalysts are extremely sensitive to air and moisture to varying degrees. Coordination catalysts are typically reduced in their activity or irreversibly destroyed by access to (atmospheric) oxygen and/or water. Most Ziegler-Natta and metallocene catalysts, for example, deactivate spontaneously on access to air and become unusable. Most coordination catalysts must therefor typically be protected from access to air and moisture during preparation, storage and use, which of course makes handling difficult and increases the cost to make polymer product using these catalysts.
An additional factor to be considered is the ability to utilize the coordination catalyst as a heterogeneous catalyst system. The advantages of a heterogeneous catalyst system are more fully realized in a slurry and gas phase polymerization processes. For example, slurry polymerizations are often conducted in a reactor wherein monomer, catalysts, and diluent are continuously fed into the reactor. The solid polymer that is produced is not dissolved in the diluent and is allowed to settle out before being periodically withdrawn from the reactor. In this kind of polymerization, factors other than activity and selectivity, which are always present in solution processes, become of paramount importance.
For example, in the slurry process it is desired to have a supported catalyst that produces relatively high bulk density polymer. If the bulk density is too low, the handling of the solid polymer becomes impractical. It is also an advantage to have the polymer formed as uniform, spherical particles that are relatively free of fines. Although fines can have a high bulk density, they do not settle as well as larger particles and thus present additional handling problems with the later processing of the polymer fluff.
Furthermore, slurry polymerization processes differ in other fundamental ways from the typical solution polymerization processes. Solution polymerization is normally conducted at high reaction temperatures (>130° C.) and pressure (>450 psi) which often results in lower molecular weight polymers. The lower molecular weight is attributed to the rapid chain-termination rates under such reaction conditions. Although lowering the reaction temperature and/or pressure, or changing molecular structure of the catalyst used in a solution process may produce higher molecular weight polymer, it becomes impractical to process the resulting high molecular weight polymers in the downstream equipment due to the high viscosity.
In contrast, a slurry reaction process overcomes many of the above disadvantages by simply operating at lower temperature (<110° C.). As a result, a higher molecular weight polymer with a uniform particle size and morphology can be routinely obtained. It is also advantageous to carry out slurry reactions with sufficiently high polymerization efficiencies such that residues from the polymerization catalysts do not have to be removed from the resulting polymers.
The above-discussed advantages of slurry polymerization processes provide incentive for developing coordination catalysts in heterogeneous form.
Thus, there has been a continuing search to develop a coordination catalyst system and methods of forming the same, which demonstrates high catalyst activity, are readily formed and can be produced in an inexpensive and efficient manner. Further, it is highly desired to have a coordination catalyst system which does not require an additional cocatalyst component, especially those conventionally used which are difficult, and even dangerous, to handle. Still further, there has also been a particular need to discover compounds, which are less sensitive to deactivation and/or less hazardous and still suitable as activating components in coordination catalyst systems. The present invention was developed in response to these searches.
The concerns directed to materials which are useful as a support for coordination pre-catalysts are described in WO97/48743 directed to spray-dried agglomerates of silica gel of controlled morphology and U.S. Pat. Nos. 5,395,808; 5,569,634; 5,403,799; 5,403,809 and EP 490,226 directed to formation of ultimate particles of bound clay by spray drying.
Supported catalyst systems are described in U.S. Pat. No. 5,633,419 which describes the use of spray-dried silica gel as a support for Ziegler-Natta catalyst systems; U.S. Pat. No. 5,362,825 directed to supported Ziegler-Natta catalysts formed by contacting a pillared clay material with a Ziegler-Natta catalyst composition; U.S. Pat. No. 5,807,800 directed to a supported metallocene catalyst formed by contacting a particulate support with a formed stereo specific metallocene ligand; U.S. Pat. No. 5,238,892 directed to use of undehydrated silica as support for metallocene and activator; and U.S. Pat. No. 5,308,811 directed to formation of supported metallocene-type transition metal compound by contacting it with a clay and an organoaluminum compound.
WO 0125149 A2 discloses a composition comprising an acid treated cation exchanging layered substrate material dispersed in silica gel as a support for a metallocene polymerization catalyst. Acidification is accomplished using a Bronsted acid such as sulfuric acid or an acidified amine, e.g., ammonium sulfate in a mixture with alkaline metal silicate such that the latter precipitates as silica hydrogel. The resulting slurry is dried, e.g., spray dried, and contacted with a metallocene catalyst. Preferably the layered silicate material is fully acid exchanged.
WO 0149747A1 discloses a supported catalyst composition comprising an organoaluminum compound, an organometal compound and an oxide matrix support wherein the latter is a mixture of an oxide precursor compound such as a silica source and a substantially decomposed (exfoliated) layered mineral such as a clay. Decomposition of the clay is achieved, for example, by solvent digestion in a strong acidic and basic medium at elevated temperatures combined with high energy or high shear mixing to product a colloidal suspension. Decomposition (exfoliation) converts the material to its residual mineral components and is said to be complete when the layered mineral no longer has its original layered structure.
WO 0142320 discloses a clay or expanded clay useful as a polymerization catalyst support. The support comprises the reaction product of the clay or expanded clay with an organometallic, or organometalloid, compound in order to reduce, cap or remove residual hydroxyl or other polar functionality of the clay and replace such groups with the organometallic compound. An organometallic or organometalloid derivative is bound to the support through the support oxygen or other polar functionality. Prior to reaction with the organometallic compound, the clay can be ion exchanged to replace at least a portion of alkali or alkali earth metal cations, e.g. sodium or magnesium, originally present in the clay. The chemically modified clay may be calcined either before or after treatment with the organometallic compound; prior treatment is preferred. The organometallic or organometalloid compound contains Mg, Zn or boron, preferably Zn, and the organic group preferably is a C1-C10 alkyl.
The teachings of intercalated clays as support materials for catalytic compositions include; U.S. Pat. No. 5,753,577 (directed to a polymerization catalyst comprising a metallocene compound, a co-catalyst such as proton acids, ionized compounds, Lewis acids and Lewis acidic compounds, and a clay mineral); U.S. Pat. No. 5,399,636 (directed to a composition comprising a bridged metallocene which is chemically bonded to an inorganic moiety such as clay or silica); EP 849,292 (directed to an olefin polymerization catalyst consisting essentially of a metallocene compound, a modified clay compound, and an organoaluminum compound); U.S. Pat. No. 5,807,938 (directed to an olefin polymerization catalyst obtained by contacting a metallocene compound, an organometallic compound, and a solid component comprising a carrier and an ionized ionic compound capable of forming a stable anion on reaction with the metallocene compound); U.S. Pat. No. 5,830,820 and EP 881,232 (directed to an olefin polymerization catalyst comprising a metallocene compound, and an organoaluminum compound and a clay mineral which has been modified with a compound capable of introducing a cation into the layer interspaces of the clay); EP 849,288 (discloses an olefin polymerization catalyst consisting essentially of metallocene compound, an organoaluminum compound, and a clay compound that has been modified with a proton acid); and U.S. Pat. No. 4,761,391 (directed to delaminated clays whose x-ray defraction patterns do not contain a distinct first order reflection. These clays are made by reacting swelling clays with a pillaring agent.) The ratio of clay to pillaring agents is disclosed to be between about 0.1 and about 10. To obtain the delaminated clay, a suspension of swelling clay, having the proper morphology, e.g., colloidal particle size, is mixed with a solution or a suspension of the pillaring agent at the aforedescribed ratios. As the reactants are mixed, the platelets of clay rapidly sorb the pillaring agent producing a flocculated mass.
Additional patents, which disclose intercalated clays, are U.S. Pat. Nos. 4,375,406; 4,629,712 and 4,637,992. Additional patents, which disclose pillared clays, include U.S. Pat. Nos. 4,995,964 and 5,250,277.
PCT International Application No. PCT/US96/17140, corresponding to U.S. Ser. No. 562,922, discloses a support for metallocene olefin polymerization comprising the reaction product of an inorganic oxide comprising a solid matrix having reactive hydroxyl groups or reactive silane functionalized derivatives of hydroxyl groups on the surface thereof, and an activator compound. The activator compound comprises a cation which is capable of reacting with a metallocene compound to form a catalytically active transition metal complex.
U.S. Pat. No. 5,880,241 discloses various late transition metal bidentate catalyst compositions. At column 52, lines 18 et seq., it is disclosed that the catalyst can be heterogenized through a variety of means including the use of heterogeneous inorganic materials as non-coordinating counter ions. Suitable inorganic materials disclosed include aluminas, silicas, silica/aluminas, cordierites, clays, and MgCl2 but mixtures are not disclosed. Spray drying the catalyst with its associated non-coordinating anion onto a polymeric support is also contemplated. Examples 433 and 434 employ montmorillonite clay as a support but polymer morphology is not disclosed for these examples.
PCT International Application No. PCT/US97/23556 discloses a process for polymerizing ethylene by contact with Fe or Co tridentate ionic complex formed either through alkylation or abstraction of the metal alkyl by a strong Lewis acid compound, e.g., MAO, or by alkylation with a weak Lewis acid, e.g., triethylaluminum and, subsequent abstraction of the resulting alkyl group on the metal center with a stronger Lewis acid, e.g., B(C6F5)3.
U.S. Ser. No. 09/166,545, filed Oct. 5, 1998, by Keng-Yu Shih, an inventor of the present application, discloses a supported late transition metal bidentate or tridentate catalyst system containing anion and cation components wherein the anion component contains boron, aluminum, gallium, indium, tellurium and mixtures thereof covalently bonded to an inorganic support (e.g., SiO2) through silane derived intermediates such as silica-tethered anilinium borate.
U.S. Ser. No. 09/431,803 by Keng-Yu Shih discloses the use of silica agglomerates as a support for transition metal catalyst systems employing specifically controlled (e.g., very low) amounts of non-abstracting aluminum alkyl activators.
U.S. Ser. No. 09/432,008 by Keng-Yu Shih et al. discloses the use of a support-activator in agglomerate form used with metallocene and/or constrained geometry coordination catalyst components and methods of their preparation.
U.S. Ser. No. 09/431,771 by Keng-Yu Shih et al discloses the use of a support-activator in agglomerate form and coordination catalyst systems based on certain transition metal compounds in combination with organometallic compounds of Group 13 of the Periodic Table of Elements.
In general, the above Shih et al. teachings utilize a supported catalyst system that requires the formation of the pre-catalyst component and then applying the same by deposition or chemical bonding the pre-catalyst to a support material. Thus, one first forms and isolates the pre-catalyst compound for subsequent application to an inorganic oxide support. Both the pre-catalyst and activator agents must be carefully handled to prevent their deactivation.
The following documents are known to the present inventors:
U.S. provisional application Ser. No. 60/287,601, filed on Apr. 30, 2001, discloses catalyst composition composed of a support-activator agglomerate comprising i) at least one inorganic oxide component, and ii) at least one ion-containing layered component, and the agglomerate has chromium atoms covalently immobilized thereon and therein.
U.S. provisional application Ser. No. 60/287,602, filed on Apr. 30, 2001, discloses a catalyst composition composed of a support-activator agglomerate comprising i) at least one inorganic oxide component, and ii) at least one ion-containing layered component. The agglomerate is a support activator for a combination of catalysts comprising at least one metallocene catalyst and at least one coordination catalyst of a bidentate or tridentate pre-catalyst transition metal compound.
U.S. provisional application Ser. No. 60/287,617, filed on Apr. 30, 2001, discloses a process for forming a catalyst composition comprising substantially simultaneously contacting at least one bidentate ligand forming compound or at least one tridentate ligand forming compound or mixtures thereof with a transition metal compound and with a support-activator agglomerate comprising i) at least one inorganic oxide component, and ii) at least one ion-containing layered component and the agglomerate has chromium atoms covalently bonded to oxygen atoms of the inorganic oxide. The reference is further directed to the resultant catalyst composition for which the support-activator agglomerate functions as the activator for the catalyst system.
U.S. provisional application Ser. No. 60/287,600, filed on Apr. 30, 2001, discloses a catalyst composition composed of a support-activator agglomerate comprising i) at least one inorganic oxide component, and ii) at least one ion-containing layered component and the agglomerate has chromium atoms covalently bonded to oxygen atoms of the inorganic oxide. The agglomerate provides a support for at least one coordination catalyst comprising a pre-catalyst composed of a bidentate or tridentate ligand containing transition metal compound.
Additional patent applications known to the inventors are concurrently filed and copending U.S. applications having Ser. No. 10/120,289; Ser. No. 10/120,317; Ser. No. 10/120,331; Ser. No. 10/120,310; and Ser. No. 10/120,314. The teachings of each of the above cited provisional applications and concurrently filed applications are incorporated herein in their entirety by reference.